Hybrid fiber/coaxial (HFC) communications systems transmit signals in a forward and reverse path between a headend and a plurality of subscribers. In the reverse path, a coaxial cable feeder portion connects the subscriber equipment (i.e., customer premise equipment (CPE)), with an optical node, which converts the radio frequency (RF) signals received from the CPE to optical signals, that sits at the input of an optical link. Subsequently, the optical link connects the reverse path from the optical node to a hub or headend. Typically, a cable modem termination system (CMTS) located in the hub or headend receives the reverse signals and processes them accordingly.
There is a significant variability and uncertainty in reverse signal loss in the coaxial feeder portion of the system between various subscriber locations and the input to the optical link. The resulting RF subcarrier level uncertainty can then cause a dynamic control overdrive or underdrive condition of the optical link. Unfortunately, the actual dynamic control of the level of these RF subcarriers is mostly done at the input of a CMTS blade, which is at the far end of the reverse path (i.e., in the hub or headend) and is typically referred to as long-loop automatic gain control (AGC), by sending a control signal commanding the CPE to increase or decrease the power level of the RF subcarrier signals. Therefore, there is a need to shift the control and the monitoring of the level of reverse RF subcarriers from the CMTS blade closer to the input of the optical link where these levels are most critical.